Pump apparatus

ABSTRACT

A pump apparatus is provided with a tank in which a handled-fluid having insulating properties is stored, and with a pump that is mounted in the tank. The pump has an impeller in which a magnet is embedded, a motor stator that is disposed at a position opposing the magnet, a pump casing that houses the impeller, and a motor casing that houses the motor stator. The motor casing is open such that a winding of the motor stator is immersed in the handled-fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority Patent Application JP 2017-254071 filed on Dec. 28, 2017, the entire contents of which are incorporated herein by reference.

FIELD

The present technology relates to a pump apparatus.

BACKGROUND AND SUMMARY

Conventionally, a handled-fluid (heated medium) used for cooling or regulating the temperature of an external apparatus such as semiconductor manufacturing apparatus is circulated between a tank in which the handled-fluid is stored and a heat exchange part of the external apparatus using a pump.

This kind of pump is often mounted outside of the tank (to a side part or lower part the tank), and as a result, particularly in cases in which the pump is mounted at the side of the tank and the like, the overall apparatus tends to be increased in size. JP 2005-330901 A discloses a vertical multistage pump in which a motor section of the pump is mounted to an upper part of a tank.

Further, in cases in which a fluorine-based insulating fluid is used as the handled-fluid (heated medium), the handled-fluid itself is expensive. In addition, a gas detector for detecting toxic gas used in manufacturing processes is mounted in semiconductor manufacturing facilities, and leakage of the handled-fluid sometimes causes the gas detector to make a false detection. Accordingly, there are cases in which a canned motor pump, which will not leak fluid, is used for the pump that circulates handled-fluid.

However, since canned motor pumps have a structure whereby heat generated by the motor is cooled by the handled-fluid, in cases in which the circulation temperature of the handled-fluid is comparatively high and the like, the temperature of the motor rises. Accordingly, fluid circulation or air purging for forcibly cooling the motor from the outside is sometimes necessary, and the overall apparatus tends to be further increased in size.

It is desirable to provide a pump apparatus that is capable of accommodating handled-fluid of a comparatively high temperature without increasing the size of the overall apparatus.

A pump apparatus according to one embodiment includes:

a tank in which a handled-fluid having insulating properties is stored; and

a pump that is mounted in the tank, wherein

-   -   the pump has         -   an impeller in which a magnet is embedded,         -   a motor stator that is disposed at a position opposing the             magnet,         -   a pump casing that houses the impeller, and         -   a motor casing that houses the motor stator, and     -   the motor casing is open such that a winding of the motor stator         is immersed in the handled-fluid.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of a pump apparatus according to a first embodiment;

FIG. 2 is an enlarged cross-sectional diagram illustrating a pump of the pump apparatus illustrated in FIG. 1;

FIG. 3 is a plan view of the pump illustrated in FIG. 2 as viewed from an intake side; and

FIG. 4 is a schematic diagram illustrating a configuration of a pump apparatus according to a second embodiment.

DETAILED DESCRIPTION OF NON-LIMITING EXAMPLE EMBODIMENTS

A pump apparatus according to a first aspect of an embodiment includes:

a tank in which a handled-fluid having insulating properties is stored; and

a pump that is mounted in the tank, wherein

-   -   the pump has         -   an impeller in which a magnet is embedded,         -   a motor stator that is disposed at a position opposing the             magnet,         -   a pump casing that houses the impeller, and         -   a motor casing that houses the motor stator, and     -   the motor casing is open such that a winding of the motor stator         is immersed in the handled-fluid.

According to this aspect, since the pump is mounted in the tank, the overall apparatus can be made more compact. Further, since the motor casing is open and the windings of the motor stator are immersed in the handled-fluid in the tank, the windings can be directly cooled by the handled-fluid, and the efficiency by which the windings are cooled is improved. Thus, since increases in the temperature of the windings can be reduced, it is possible to increase pump performance and raise an upper limit for handled-fluid temperature.

Further, according to this aspect, a casing body can be simplified due to, for example, conventional motor casing parts and the waterproof connector used at the power supply connection becoming unnecessary, and costs are able to be reduced. Further, in comparison to conventional cases in which a motor is cooled by the flow of air, air purging is unnecessary, and so an energy-saving effect is obtained, the apparatus can be made more compact, the number of components such as cooling fins and manifolds can be cut, and the overall apparatus is able to be simplified due to, for example, airflow control becoming unnecessary.

Moreover, according to this aspect, as a result of the pump being mounted in the tank and immersed in the handled-fluid, and of the tank serving a dual role as the casing body, noise is able to be reduced.

A pump apparatus according to a second aspect of an embodiment is the pump apparatus according to the first aspect, wherein

a guide is disposed on an intake side of the pump, the guide guiding the handled-fluid such that the handled-fluid passes through a position where the motor casing is open.

According to this aspect, the handled-fluid is guided by the guide so as to pass through the position where the motor casing is open, and in the vicinity of the windings of the motor stator, even if the temperature of the handled-fluid increases due to heat generated by the windings, since the handled-fluid with the increased temperature does not stay in this location, the efficiency by which the windings are cooled by the handled-fluid can be raised even further.

A pump apparatus according to a third aspect of an embodiment is the pump apparatus according to the first aspect or the second aspect, wherein

an intake port of the pump is disposed at a higher height position than the motor stator.

According to this aspect, a state can be maintained in which the windings of the motor stator are immersed in the handled-fluid and are directly cooled while the pump is running normally.

A pump apparatus according to a fourth aspect of an embodiment is the pump apparatus according to the third aspect, further including:

a controller that monitors current supplied to the motor stator, and in cases in which the current supplied to the motor stator falls below a prescribed threshold, the controller performs at least one operation out of stopping the supply of current to the motor stator or issuing an alert.

According to this aspect, in cases in which the windings are not immersed in the handled-fluid and the windings cannot be efficiently cooled by the handled-fluid, an excessive increase in the temperature of the windings when the pump is continually run can be prevented.

Detailed description follows regarding specific examples of embodiments, with reference to the accompanying drawings. Note that in the drawings accompanying the present specification, as appropriate, the scale, length and width, and other dimensional ratios are modified and exaggerated compared to those in actuality in order to facilitate understanding of the illustrations.

FIG. 1 is a schematic diagram illustrating the configuration of a pump apparatus 1 according to a first embodiment. As illustrated in FIG. 1, the pump apparatus 1 is provided with a tank 10, and with a pump 20 that is mounted in the tank 10.

A handled-fluid 11 that has insulating properties is stored in the tank 10. A fluorine-based insulating fluid (specifically, for example, Fluorinert (registered trademark)) is, for example, employed as the handled-fluid 11.

In the example illustrated, a feed pipe 14 is inserted and installed in a lower side wall of the tank 10, and a discharge pipe 20 c of the pump 20 is connected to the feed pipe 14 via a fitting 15. In order to facilitate pipe connection/disconnection in the tank 10, a union fitting or a ferrule fitting is preferable employed as the fitting 15. Handled-fluid 11 discharged from the discharge pipe 20 c of the pump 20 is fed through the feed pipe 14 and to a non-illustrated external apparatus.

A return pipe 13 is inserted and installed in the ceiling of the tank 10. Handled-fluid 11 that has passed through the non-illustrated external apparatus so as to perform heat exchange returns through the return pipe 13 to the inside of the tank 10, where the handled-fluid 11 is stored.

FIG. 2 is an enlarged cross-sectional diagram illustrating the pump 20 mounted in the tank 10. As illustrated in FIG. 2, the pump 20 has an impeller 21 in which magnets (permanent magnets) 22 are embedded, a motor stator 23 that is disposed at a position opposing the magnets 22, a pump casing 24 that houses the impeller 21, and a motor casing 25 that houses the motor stator 23. Fluid-contacting parts of the pump casing 24 and the motor casing 25 are formed from a material that is resistant to the handled-fluid 11, for example a resin such as polyphenylene sulfide (PPS) or a polyether ether ketone (PEEK).

As illustrated in FIG. 2, the motor stator 23 and the motor casing 25 are disposed on an intake side of the impeller 21, and the motor casing 25 defines an intake port 20 a. A bearing assembly 26 is disposed between the motor casing 25 and the impeller 21. The bearing assembly 26 supports radial loading and thrust loading from the impeller 21.

As illustrated in FIG. 2, a respective fluid flow path is formed in a central part of each of the motor casing 25 and the bearing assembly 26. The fluid flow paths are joined in series so as to configure a single fluid flow path extending from the intake port 20 a to a fluid inlet of the impeller 21. The fluid flow paths are in communication with the fluid inlet of the impeller 21.

The pump 20 according to the present embodiment is a pump equipped with an axial-gap PM motor, in which the magnets 22 and the motor stator 23 are disposed along the fluid flow paths.

As illustrated in FIG. 2, the discharge pipe 20 c, which has a discharge port 20 b, is provided in a side face of the pump casing 24. Fluid having increased pressure due to the rotating impeller 21 is discharged through the discharge pipe 20 c and from the discharge port 20 b. Note that the pump 20 according to the present embodiment is what is known as an end-top pump, in which the intake port 20 a and the discharge port 20 b are orthogonal to one another.

The impeller 21 is formed from a nonmagnetic material that slides easily, is not susceptible to wear, and that is resistant to the handled-fluid 11. For example, a resin such as polyphenylene sulfide (PPS) or a polyether ether ketone (PEEK), or a ceramic, is suited to be employed as the material of the impeller 21. The pump casing 24 and the motor casing 25 can also be formed from the same material as the impeller 21.

The impeller 21 is rotatably supported by the single bearing assembly 26. The bearing assembly 26 is a slide bearing (dynamic pressure bearing) that makes use of fluid dynamic pressure. The bearing assembly 26 is configured by a combination of a rotating-side bearing 26 a and a stationary-side bearing 26 b that loosely engage with one another.

The rotating-side bearing 26 a is fixed to the impeller 21, and is disposed so as to surround the fluid inlet of the impeller 21. The stationary-side bearing 26 b is fixed to the motor casing 25, and is disposed on the intake side of the rotating-side bearing 26 a. The stationary-side bearing 26 b has a cylindrical part that extends along an axial direction of the rotating-side bearing 26 a, and a flange that projects outward from the cylindrical part.

The cylindrical part of the stationary-side bearing 26 b has a radial face that supports radial loading from the impeller 21, and the flange of the stationary-side bearing 26 b has a thrust face that supports thrust loading from the impeller 21. The radial face is parallel to the axis of the impeller 21, and the thrust face is perpendicular to the axis of the impeller 21. The rotating-side bearing 26 a is disposed around the cylindrical part of the stationary-side bearing 26 b.

Some of the handled-fluid 11 that is discharged from the impeller 21 passes is introduced into the bearing assembly 26 through a small gap between the impeller 21 and the motor casing 25. When the rotating-side bearing 26 a rotates together with the impeller 21, fluid dynamic pressure arises between the rotating-side bearing 26 a and the stationary-side bearing 26 b, whereby the impeller 21 is supported by the bearing assembly 26 in a state of non-contact therewith. Since the stationary-side bearing 26 b supports the rotating-side bearing 26 a using the radial face and the thrust face that are orthogonal to one another, tilting of the impeller 21 is restricted by the bearing assembly 26.

The motor stator 23 has a core 23 a and a plurality of windings (coils) 23 b. The plurality of windings 23 b are disposed in a ring shape. The impeller 21 and the motor stator 23 are disposed concentrically to the bearing assembly 26 and the intake port 20 a.

Lead wires 23 c are connected to the windings 23 b of the motor stator 23 via a wiring substrate 23 d. Referring to FIG. 1, a power supply connector 12 is attached to an upper side wall of the tank 10, and the windings 23 b of the motor stator 23 are electrically connected to an inverter device 3 via the lead wires 23 c, the wiring substrate 23 d, and the power supply connector 12. In addition to being connected to a power supply 2, the inverter device 3 is also connected to a control device (controller) 4 that controls operation of the inverter device 3.

The inverter device 3 supplies current to the windings 23 b of the motor stator 23 so as to cause the motor stator 23 to generate a rotating magnetic field. The rotating magnetic field acts on the magnets 22 embedded in the impeller 21, and rotationally drives the impeller 21. The torque of the impeller 21 depends on the magnitude of the current supplied to the motor stator 23. So long as the load exerted on the impeller 21 is constant, the current supplied to the motor stator 23 is substantially constant.

When the impeller 21 rotates, the handled-fluid 11 stored in the tank 10 is introduced into the fluid inlet of the impeller 21 through the intake port 20 a. The handled-fluid 11 has increased pressure due to rotation of the impeller 21, and the handled-fluid 11 is discharged from the discharge port 20 b. While the impeller 21 is moving the handled-fluid 11, the back face of the impeller 21 is pushed toward the intake side (namely, toward the intake port 20 a) by fluid having increased pressure. The bearing assembly 26 is disposed on the intake side of the impeller 21, and so the bearing assembly 26 supports thrust loading from the impeller 21 from the intake side.

In the present embodiment, as illustrated in FIG. 1 and FIG. 2, the motor casing 25 is open such that the windings 23 b of the motor stator 23 are immersed in the handled-fluid 11. Reference numeral 25 a indicates the opening in the motor casing 25. The motor casing 25 is open on the intake side (the upper side in the drawings) of the pump 20.

FIG. 3 is a plan view of the pump 20 as viewed from the intake side. In FIG. 3, reference numeral 25 a 1 indicates an inner circumference of the opening 25 a in the motor casing 25, and reference numeral 25 a 2 indicates an outer circumference of the opening 25 a in the motor casing 25. The region between the inner circumference 25 a 1 and the outer circumference 25 a 2 is the opening 25 a. In the example illustrated in FIG. 3, the wiring substrate 23 d for wiring the lead wires 23 c extending from the power supply connector 12 to the windings 23 b is disposed in the opening 25 a in the motor casing 25, and a plurality of notches 23 e are formed in each of an outer circumferential edge and an inner circumferential edge of the wiring substrate 23 d. The plurality of notches 23 e are formed spaced apart (for example, at evenly spaced intervals) along a circumferential direction. The handled-fluid 11 stored in the tank 10 flows through the opening 25 a in the motor casing 25, through the notches 23 e in the wiring substrate 23 d, into the motor casing 25, and the windings 23 b are directly immersed in the handled-fluid 11.

Note that the wiring substrate 23 d is not absolutely necessary, and the wiring substrate 23 d may be omitted, or the lead wires 23 c extending from the power supply connector 12 may be directly wired to the windings 23 b. In such cases, the handled-fluid 11 stored in the tank 10 flows straight into the motor casing 25 through the opening 25 a in the motor casing 25, and the windings 23 b are directly immersed in the handled-fluid 11.

When current flows into the windings 23 b of the motor stator 23 when the pump 20 is run, heat is generated due to the electrical resistance of the windings 23 b. However, in the present embodiment, since the motor casing 25 is open and the windings 23 b of the motor stator 23 are immersed in the handled-fluid 11 in the tank 10, the windings 23 b can be directly cooled by the handled-fluid 11, and the windings 23 b can be efficiently cooled. Note that in the present embodiment, since the handled-fluid 11 is a fluid that has electrically insulating properties, the windings 23 b are not shorted together by immersion in the handled-fluid 11.

As illustrated in FIG. 1 and FIG. 2, the intake port 20 a of the pump 20 may be disposed at a higher height position than the motor stator 23. This enables a state to be maintained in which the windings 23 b of the motor stator 23 are immersed in the handled-fluid 11 and are directly cooled while the pump 20 is being operated.

Referring to FIG. 1, a control device 4 that controls operation of the inverter device 3 monitors the current supplied to the motor stator 23 from the inverter device 3, and in cases in which the current supplied to the motor stator 23 falls below a prescribed threshold, the control device 4 performs at least one operation out of stopping the supply of current to the motor stator 23 or issuing an alert.

For example, the control device 4 decides whether or not the pump 20 is being run with an abnormal level of current, namely, in a dry state or in a state having insufficient fluid, on the basis of a rate of change in current and/or a change in current value. So long as the pump 20 is immersed in the handled-fluid 11 and the handled-fluid 11 is present in the pump 20, a rate of change in current and/or a change in current value are effectively zero.

If the pump 20 is run in a dry state or in a state having insufficient fluid (run empty), the current supplied to the motor stator 23 is reduced. The control device 4 makes a comparison between a rate of change in current and/or a change in current value and a prescribed threshold. Herein, prescribed threshold is a general term for a value indicated in the following (a number of times going under a reference value, a set value, a regulation value, a number of times going under a tolerance value or an amount of deviation, etc.).

More specifically, when the pump 20 is run in a dry state or in a state having insufficient fluid, since the motive power of the pump 20 is reduced, the current supplied to the motor stator 23 from the inverter device 3 is reduced. Namely, in cases in which no fluid is present in the pump 20, since minimal load is exerted on the impeller 21, minimal current is supplied to the motor stator 23. Thus, the control device 4 monitors the current supplied to the motor stator 23, and calculates a rate of change in current for a prescribed time interval. In one embodiment, per prescribed time interval (for example, one month), the control device 4 may calculate a rate of change in current for this prescribed time interval.

Then, the control device 4 decides whether or not the pump 20 is being run with an abnormal level of current, namely, in a dry state or in a state having insufficient fluid, on the basis of the current supplied to the motor stator 23. An abnormal level of current can, for example, be defined as follows. Namely, a value, such as an average value obtained from current values while the pump 20 was running normally, is set in advance as a reference value. Then, this reference value is employed to compute a rate of change in the current being supplied. When the value of this rate of change has gone negative a prescribed number of times, the control device 4 determines there to be an abnormal level of current. In one embodiment, the control device 4 may determine there to be an abnormal level of current in cases in which the rate of change in current has fallen below a prescribed set value.

In another embodiment, after the pump 20 starts running, the control device 4 measures a current value over a prescribed amount of time, and the control device 4 may determine there to be an abnormal level of current in cases in which a value for a deviation between a past measurement value for current and a present measurement value for current has fallen below a prescribed regulation value. In such cases, rather than a rate of change in current, a change in current is computed. The change in current is the value for this deviation. In yet another embodiment, the control device 4 may determine there to be an abnormal level of current on the basis of the number of times the value for this deviation has fallen below a prescribed tolerance value, or on an amount of deviation. The regulation value and the tolerance value may be identical values, or may be different values to one another.

In cases in which a rate of change in current and/or a change in current value exceeds a prescribed threshold and then is reduced, the control device 4 transmits a control signal to the inverter device 3 and stops the supply of current to the motor stator 23. Thereby, in a state in which the pump 20 is not immersed in the handled-fluid 11, namely, in a state in which the windings 23 b of the motor stator 23 cannot be directly cooled by the handled-fluid 11, an excessive increase in temperature due to heat generated by the windings 23 b when current is supplied to the motor stator 23 can be prevented.

Further, in cases in which a rate of change in current and/or a change in current value exceeds the prescribed threshold and is then reduced, in addition to stopping current supply to the motor stator 23, or in place thereof, the control device 4 may issue an emergency alert and request an immediate response from supervising personnel.

According to the present embodiment as described above, since the pump 20 is mounted in the tank 10, the overall apparatus can be made more compact. Further, since the motor casing 25 is open and the windings 23 b of the motor stator 23 are immersed in the handled-fluid 11 in the tank 10, the windings 23 b can be directly cooled by the handled-fluid 11, and the efficiency by which the windings 23 b are cooled is improved. Thus, since increases in the temperature of the windings 23 b can be reduced, it is possible to increase pump performance and raise an upper limit for handled-fluid temperature.

Further, according to the present embodiment, a casing body can be simplified due to, for example, conventional motor casing parts and the waterproof connector used at the power supply connection becoming unnecessary, and costs are able to be reduced. Further, in comparison to conventional cases in which a motor is cooled by the flow of air, air purging is unnecessary, and so an energy-saving effect is obtained, the apparatus can be made more compact, the number of components such as cooling fins and manifolds can be cut, and the overall apparatus is able to be simplified due to, for example, airflow control becoming unnecessary.

Further, according to the present embodiment, as a result of the pump 20 being mounted in the tank 10 and immersed in the handled-fluid 11, and of the tank 10 serving a dual role as the casing body, noise is able to be reduced.

Further, according to the present embodiment, since the intake port 20 a of the pump 20 is disposed at a higher height position than the motor stator 23, a state can be maintained in which the windings 23 b of the motor stator 23 are immersed in the handled-fluid 11 and are directly cooling while the pump 20 is running normally.

Further, according to the present embodiment, since the control device 4 monitors the current supplied to the motor stator 23, and in cases in which the current supplied to the motor stator 23 falls below a prescribed threshold, the control device 4 performs at least one operation out of stopping the supply of current to the motor stator 23 or issuing an alert, in cases in which the windings 23 b are not immersed in the handled-fluid 11 and the windings 23 b cannot be efficiently cooled by the handled-fluid 11, an excessive increase in the temperature of the windings 23 b when the pump 20 is continually run can be prevented.

Detailed description has been given regarding the first embodiment. However, the present technology is not limited to the above embodiment, and various modifications to the above embodiment are possible. In the following, a modified example will be described with reference to the drawings. In the following description, and in the drawings employed by the following description, reference numerals identical to the reference numerals employed for corresponding portions in the above embodiment will be employed for portions that are able to be configured similarly to in the above embodiment, and duplicate explanation thereof will be omitted.

FIG. 4 is a schematic diagram illustrating the configuration of a pump apparatus 1′ according to a second embodiment.

In the second embodiment, a guide 29 is disposed on the intake side of the pump 20. The guide 29 guides the handled-fluid 11 such that the handled-fluid 11 passes through a position where the motor casing 25 is open. In the example illustrated, the guide 29 has a flat plate shape, is spaced above the intake port 20 a, and is disposed so as to face both the intake port 20 a and the opening 25 a of the motor casing 25.

When the pump 20 starts running, handled-fluid 11 in the tank 10 is sucked from a gap between the motor casing 25 and the guide 29, passes through the position where the motor casing 25 is open, and into the intake port 20 a.

According to this aspect, in the vicinity of the windings 23 b of the motor stator 23, even if the temperature of the handled-fluid 11 increases due to heat generated by the windings 23 b, since the handled-fluid 11 with the increased temperature does not stay in this location, the efficiency by which the windings 23 b are cooled by the handled-fluid 11 can be raised even further.

Note that although the pump 20 is mounted in a vertical orientation (with the intake port 20 a pointing upward) in the tank 10 in the above embodiments, there is no limitation thereto, and depending on the shape of the tank 10 and the like, the pump 20 may be set in a horizontal orientation (with the intake port 20 a pointing sideways) in the tank 10.

Further, although in the above embodiments configuration is such that the control device 4 calculates a rate of change in the current supplied to the motor stator 23, and in cases in which the current falls below a prescribed threshold and the pump 20 is judged to be in a state running empty, the control device 4 performs at least one operation out of stopping the supply of current to the motor stator 23 or issuing an alert, there is no limitation thereto.

For example, configuration may be such that the control device 4 monitors a measurement value from a non-illustrated flow rate sensor provided to the feed pipe 14 or the like, and in cases in which the flow rate falls below a prescribed threshold and the pump 20 is judged to be in a state running empty, the control device 4, the control device 4 performs at least one operation out of stopping the supply of current to the motor stator 23 or issuing an alert.

Further, for example, configuration may be such that the control device 4 monitors a measurement value from a non-illustrated water level sensor provided in the tank 10, and in cases in which the water level in the tank 10 falls below a prescribed threshold (for example, the height position of the intake port 20 a) and the pump 20 is judged to be in a state running empty, the control device 4, the control device 4 performs at least one operation out of stopping the supply of current to the motor stator 23 or issuing an alert.

According to this aspect, in cases in which the windings 23 b are not immersed in the handled-fluid 11 and the windings 23 b cannot be efficiently cooled by the handled-fluid 11, an excessive increase in the temperature of the windings 23 b when the pump 20 is continually run can be prevented.

Although embodiments of the present technology have been described by way of example, the scope of the present technology is not limited to these embodiments, and it goes without saying that various changes and modifications may be implemented as appropriate according to usage within the scope set forth in the claims. 

What is claimed is:
 1. A pump apparatus comprising: a tank in which a handled-fluid having insulating properties is stored; and a pump that is mounted in the tank, wherein the pump has an impeller in which a magnet is embedded, a motor stator that is disposed at a position opposing the magnet, a pump casing that houses the impeller, and a motor casing that houses the motor stator, and the motor casing is open such that a winding of the motor stator is immersed in the handled-fluid.
 2. The pump apparatus according to claim 1, wherein a guide is disposed on an intake side of the pump, the guide guiding the handled-fluid such that the handled-fluid passes through a position where the motor casing is open.
 3. The pump apparatus according to claim 1, wherein an intake port of the pump is disposed at a higher height position than the motor stator.
 4. The pump apparatus according to claim 3, further comprising: a controller that monitors current supplied to the motor stator, and in cases in which the current supplied to the motor stator falls below a prescribed threshold, the controller performs at least one operation out of stopping the supply of current to the motor stator or issuing an alert. 